1. Field of the Invention
The present invention relates to a method of manufacturing an exhaust gas purifying apparatus, and an exhaust gas purifying apparatus.
2. Discussion of the Background
In order to purify harmful substances such as toxic gases contained in exhaust gas discharged from an internal combustion engine such as an engine, conventionally an exhaust gas purifying apparatus is installed in an exhaust path (exhaust pipe for exhaust gas distribution, and the like) of the internal combustion engine.
The exhaust gas purifying apparatus has a structure in which a casing is provided in the exhaust path of the internal combustion engine, and an exhaust gas-treating body is disposed inside the casing. Examples of the exhaust gas-treating body include a catalyst carrier or a diesel particulate filter (DPF).
For improving the efficiency of purifying harmful substances of the exhaust gas purifying apparatus in which a catalyst is supported on the exhaust gas-treating body, temperatures in the exhaust path of the internal combustion engine and exhaust gas need to be maintained at temperatures suitable for activating the catalyst (hereinafter, also referred to as catalyst activation temperature).
As described earlier, the exhaust gas purifying apparatus in which a catalyst is supported on the exhaust gas-treating body tends not to exert a sufficient catalytic action unless the temperature is raised to a predetermined catalyst activation temperature. Therefore, the exhaust gas purifying apparatus soon after starting the engine problematically requires a certain period of time to achieve a sufficient level of the exhaust gas purification ability.
For solving the problems, electrically heated catalyst (EHC) converters for rapidly heating a catalyst have been proposed to reduce harmful substances discharged immediately after starting the engine.
For example, JP-A 5-269387 discloses a catalytic converter (exhaust gas purifying apparatus) in which a metallic exhaust gas-treating body is provided in a metallic shell (casing), and positive and negative electrode members connected to a metallic catalyst carrier (exhaust gas-treating body) are provided in a manner to insulatingly penetrate the metallic shell wall and project therefrom.
FIG. 1A is a cross-sectional view schematically showing a conventional exhaust gas purifying apparatus disclosed in JP-A 5-269387. FIG. 1B is a C-C line cross-sectional view of the conventional exhaust gas purifying apparatus shown in FIG. 1A.
In a conventional catalytic converter (exhaust gas purifying apparatus) 500 shown in FIG. 1A and FIG. 1B, metallic catalyst carriers (exhaust gas-treating bodies) 530a, 530b, and 530c are disposed in a metallic shell (casing) 520. The outer surfaces of the metallic catalyst carriers 530a, 530b, and 530c are respectively connected to positive electrode members 550a, 550b, and 550c, and further respectively connected to negative electrode members 550d, 550e, and 550f, with another end of each of the positive and negative electrode members penetrating the metallic shell 520.
Moreover, in the conventional catalytic converter 500 shown in FIG. 1A and FIG. 1B, ring-shaped mat members (holding sealing material) 510a, 510b, and 510c are respectively disposed between outer faces of the metallic catalyst carriers 530a, 530b, and 530c and inner faces of the metallic shell 520.
The contents of JP-A 5-269387 are incorporated herein by reference in their entirety.